SizesS (newborn to 6m), head circumference: 36 to 43cm (14" to 17")
M (6m to 12m), head circumference: 41 to 46cm (16" to 18")
L (12m to 2 years), head circumference: 44 to 48cm (17.5" to 19")
XL (2 years to 8 years), head circumference: 48 to 52cm (19" to 20.5")